An OS/2 application that has been loaded into memory and prepared for execution is called a process. A process is the code, data, and other resources of the application, such as the open file handles, semaphores, pipes, queues and so on. OS/2 considers every application it loads to be a process.
Each process has at least one thread, called the main thread or thread 1. The application runs when the system scheduler gives control to a thread in the process. For more on thread management, see Using Threads.
Note: In the example code fragments that follow, error checking was left out to conserve space. Applications should always check the return code that the functions return. Control Program functions return an APIRET value. A return code of 0 indicates success. If a non-zero value is returned, an error occurred.